Subtraction of the indirect systemic arterial systolic pressure, (in mm Hg) form the total 12-lead QRS amplitude (in mm) may provide a reasonable noninvasive prediction of the peak systolic pressure gradient across the aortic valve in patients with moderate to severe aortic valve stenosis (AS). Most studies of the electrocardiogram (ECG) in patients with AS have involved living patients in whom the status of the left ventricular myocardium, epicardial coronary arteries, and mitral valve was not precisely known. We examined the 12-lead ECG recorded within 2 months of death in 50 patients aged 16-65 years (mean age: 48) with peak systolic pressure gradients across the aortic valve in the range of 52-180 mm Hg (mean: 98) and anatomically normal mitral valves. Excluding 4 patients with complete left bundle branch block (LBBB), 44 (96 percent) of the other 46 patients had the usual voltage criteria for left ventricular hypertrophy. Measurement of the total 12-lead QRS amplitude, which ranged from 144 to 417 mm (10 mm = 1mV; mean: 257) correlated directly with the peak systolic pressure gradient across the aortic valve and, when the 4 patients with complete LBBB were excluded, with the peak left ventricular systolic pressure. The total 12-lead QRS amplitude (in mm) was similar in most patients to the left ventricular systolic pressure (in mm Hg). The mean of the total 12-lead QRS amplitude was significantly (P less than 0.05) greater in the 11 younger (less than 40 years) than in the 39 older patients (278 mm vs 257 mm), in the 14 women than in the 36 men (277 mm vs 249 mm), in the 22 patients with heavier (greater than 600 g) hearts (274 mm vs 244 mm), in the 34 patients without, compared to the 16 with, significant coronary arterial narrowing (270 mm vs 238 mm), and in the 22 patients without, compared to the 24 with, myocardial damage patterns on ECG: 269 mm vs 236 mm.